| Biodiesel,as one kind of environmental friendly and renewable high quality liquid fuel which can replace petroleum diesel,plays an important role in enhancing the energy security,decreasing the environmental pollution and restructuring the agricultural structure.In this paper,the biodiesel was prepared via transesterification of castor oil with methanol in the case of barium hydroxide as catalyst.The application of solid base barium hydroxide in transesterification of castor oil was systematically studied.Firstly,barium hydroxide was prepared from barium hydroxide octahydrate by two-stage vacuum heating dehydration and the catalyst as well as its precursor was characterized to determine the preparation conditions of solid base barium hydroxide.Results presented that the melting point of barium hydroxide octahydrate was 78°C.Barium hydroxide octahydrate dehydrated in two steps,in the first step(60-125°C)seven moles of water were lost and in the second step(near 140°C)another mole of water was lost.Barium hydroxide octahydrate was transformed into barium hydroxide by vacuum heat treatment at 70°C for three hours and then at 150°C for another ten hours.Secondly,the application of solid base barium hydroxide in transesterification of castor oil with methanol was studied and the effects of reaction conditions on reaction conversion rate were investigated.Results presented that the optimum transesterification conditions were as follows: the molar ratio of methanol to oil was 12:1,the solid base barium hydroxide dosage was 2 wt%,the reaction temperature was 50°C and the reaction time was 30 min.Under these conditions,the conversion of transesterification could reach 97.25%.The conversion of transesterification decreased with the increasing repeated times of solid base barium hydroxide.The conversion of transesterification was 82.27% when the catalyst was reused for the fifth time.Thirdly,D001 resin was used as adsorbent to remove the residual barium ion from biodiesel and the absorption properties were investigated through static and dynamic experiments.Results presented that the optimum static adsorption conditions were as follows: the biodiesel dosage was 200 g,the resin dosage was 2.0 g and the adsorption time was 8 min.Under these conditions,the barium removal rate could reach 97.58%.Hydrochloric acid solution was selected as desorption solution in the static desorption experiment.The optimum static desorption conditions were hydrochloric acid concentration of 1 mol/L and desorption time of 20 min.The barium removal rate could reach 92.41% when the resin was regenerated for the first time under these conditions.The barium removal rate decreased with the increasing regeneration times of resin in the static absorption experiment.The barium removal rate was 88.95% when the resin was regenerated for the fifth time.The biodiesel was treated by dynamic adsorption with D001 resin.In the dynamic adsorption experiment,the optimum flow velocity of biodiesel was 3 mL/min.Under this condition,the breakthrough point adsorption capacity and saturated adsorption capacity of resin could reach 53.32 mg/g and 60.51 mg/g respectively.Hydrochloric acid solution was selected as desorption solution in the dynamic desorption experiment.In the dynamic desorption experiment,barium desorption capacity could reach 59.64 mg/g and desorption rate could reach 98.56% when hydrochloric acid concentration was 1 mol/L and flow velocity was 1.5 m L/min.Lastly,the physicochemical performances of hybrid fuels were analyzed.Results presented that the density and viscosity of hybrid fuel increased but the cloud point and condensation point decreased with the increasing biodiesel content.In the case that the biodiesel content was lower than 30%,the density and viscosity of the hybrid fuel were in accordance with the standard requirements and compared with No.0 diesel oil,the hybrid fuel which has lower cloud point and lower condensation point was more favorable for the usage in the cold climate. |
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